Stray dogs and dogs in shelters are there through irresponsible owners who refuse to spay or neuter because they think it's cruel or some absurd reason, not because of professional registered breeders.
A responsible breeder should only have 3 litters per female dog, from the ages of 2-7 and one litter every other year. Puppies sold to forever pet homes are generally neutered.
It is not pedigree breeders fault, it is irresponsible owners and backyard breeders, neither of which breed pedigree dogs.